Batteries and electrochemical cells can be used as sources of energy. Generally, batteries and electrochemical cells include a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode that prevents electrical contact between the two electrodes, and an electrolytic solution in contact with the electrodes and separator that permits ion migration. Electrons flow from electrode to electrode via a conductor. The physical and chemical properties of the separator can affect the performance properties of the battery or electrochemical cell.